quantities to obtain boiler rating with the hand-fired grates, and in
order to secure a large excess over boiler rating with other coals, a
system of blowers and air ducts has been provided in the basement
under the boilers. One blower is selected for every three boilers,
with arrangements for supplying all six boilers from one blower.

The blowers are 11 feet high above the floor and 5 feet 6 inches wide
at the floor line. Each blower is direct-connected to a two crank
7-1/2 x 13 x 6-1/2-inch upright, automatic, compound, steam engine of
the self-enclosed type, and is to provide a sufficient amount of air
to burn 10,000 pounds of combustible per hour with 2 inches of water
pressure in the ash pits.

[Sidenote: _Smoke Flues
and
Economizers_]

The smoke flue and economizer construction throughout the building is
of uniform design, or, in other words, the smoke flue and economizer
system for one chimney is identical with that for every other chimney.
In each case, the system is symmetrically arranged about its
respective chimney, as can be seen by reference to the plans.

The twelve boilers for each chimney are each provided with two round
smoke uptakes, which carry the products of combustion upward to the
main smoke flue system on the economizer floor. A main smoke flue is
provided for each group of three boilers, and each pair of main smoke
flues join together on the center line of the chimney, where in each
case one common flue carries the gases into the side of the chimney.
The two common flues last mentioned enter at opposite sides of the
chimney. The main flues are arranged and fitted with dampers, so that
the gases can pass directly to the chimney, or else they can be
diverted through the economizers and thence reach the chimney.

The uptakes from each boiler are constructed of 3/8-inch plate and
each is lined with radial hollow brick 4 inches thick. Each is
provided with a damper which operates on a shaft turning in roller
bearings. The uptakes rest on iron beams at the bottom, and at the
top, where they join the main flue, means are provided to take up
expansion and contraction.

The main flue, which rests on the economizer floor, is what might be
called a steel box, constructed of 3/8-inch plate, 6 feet 4 inches
wide and 13 feet high. The bottom is lined with brick laid flat and
the sides with brick walls 8 inches thick, and the top is formed of
brick arches sprung between.

[Sidenote: _Steam Piping_]